Substrate support assembly having rapid temperature control

ABSTRACT

A substrate support assembly comprises a ceramic puck having a substrate receiving surface and an opposing backside surface. The ceramic puck has an electrode and a heater embedded therein. The heater comprises first and second coils that are radially spaced apart. A base of the support assembly comprises a channel to circulate fluid therethrough, the channel comprising an inlet and terminus that are adjacent to one another so that the channel loops back upon itself. A compliant layer bonds the ceramic puck to the base.

CROSS-REFERENCE

This application is a continuation of U.S. Non-provisional applicationSer. No. 11/778,019, filed on Jul. 14, 2007, entitled “SUBSTRATEPROCESSING WITH RAPID TEMPERATURE GRADIENT CONTROL”, which claimspriority to U.S. Provisional Application Ser. No. 60/832,545, filed Jul.20, 2006, both of which are incorporated herein by reference in theirentireties.

BACKGROUND

Embodiments of the present invention relate to processing of a substratewith rapid temperature gradient control across the substrate.

In the processing of substrates, such as semiconductors and displays, anelectrostatic chuck is used to hold a substrate in a chamber forprocessing of a layer on the substrate. A typical electrostatic chuckcomprises an electrode covered by a ceramic. When the electrode iselectrically charged, electrostatic charges accumulate in the electrodeand substrate, and the resultant electrostatic force holds the substrateto the chuck. Typically, the temperature of the substrate is controlledby maintaining helium gas behind the substrate to enhance heat transferrates across the microscopic gaps at the interface between the back ofthe substrate and the surface of the chuck. The electrostatic chuck canbe supported by a base which has channels for passing a fluidtherethrough to cool or heat the chuck. Once a substrate is securelyheld on the chuck, process gas is introduced into the chamber and aplasma is formed to process the substrate. The substrate can beprocessed by a CVD, PVD, etch, implant, oxidation, nitridation, or othersuch processes.

In such conventional substrate fabrication processes, the substrate ismaintained at a single temperature during processing. Typically, thesubstrate is passed through a slit in the chamber by a wafer blade anddeposited on lift pins which are extended through the body of theelectrostatic chuck. The lift pins are then retracted back through thechuck to deposit the substrate on the surface of the chuck. Thesubstrate quickly rises in temperature to a preset temperature which isthen maintained steady by heaters in the chuck or by the plasma formedin the chamber. The substrate temperature can be further controlled bythe temperature and flow rate of coolant passed through the channels ofthe base and below the chuck which is used to remove heat from thechuck.

While conventional processing chamber are suitable for maintaining thesubstrate at a steady single temperature during processing, they do notallow rapid changing of the temperature of the substrate during a singleprocess cycle. In certain processes, it is desirable to rapidly ramp upor down the substrate temperature, to achieve a particular temperatureprofile during the process. For example, it can be desirable to haverapid changes in substrate temperature at different stages of an etchingprocess to allow etching of different materials on the substrate atdifferent substrate temperatures. At these different etching stages, theprocess gas provided to the chamber can also change in composition orhave the same composition. As another example, in etching processes,such a temperature profile may be useful to deposit sidewall polymer onthe sidewalls of the features being etched on the substrate, and laterin the same etching process, remove the sidewalk polymer by increasingthe temperature of the etching process, or vice versa. Similarly, indeposition processes, it may be desirable to have a first processingtemperature which is higher or lower than a second processingtemperature, for example, to initially deposit a nucleating layer on thesubstrate and then grow a thermally deposited layer on the substrate.Conventional substrate processing chambers and their internal componentsoften do not allow sufficiently rapid ramp up and down of substratetemperatures.

A further complication arises when, during processing, the substrate issubjected to non-uniform process conditions in a radial direction acrossthe substrate which can give rise to non-uniform, concentric processingbands. The non-uniform processing conditions can arise from thedistribution of gas or plasma species in the chamber, which often variesdepending on the location of the inlet and exhaust gas ports in thechamber. Mass transport mechanisms can also alter the rate of arrival ordissipation of gaseous species at different regions of the substratesurface. Non-uniform processing can also occur as a result ofnon-uniform heat loads in the chamber, arising for example, from thenon-uniform coupling of energy from a plasma sheath to the substrate orfrom radiant heat reflected from chamber walls. The processing bands andother variations across the substrate are undesirable as the electronicdevices being fabricated at different regions of the substrate, forexample, the peripheral and central substrate regions, end up withdifferent properties. Accordingly, it is desirable to reduce thevariations in processing rates and other process characteristics acrossthe substrate surface during processing of the substrate.

Thus it is desirable to have a process chamber and components that allowrapid temperature ramp up and down of the substrate being processed inthe chamber. It is further desirable to control temperatures atdifferent regions across the processing surface of the substrate toreduce the effect of non-uniform processing conditions across thesubstrate surface in the radial direction. It can also be desirable tocontrol the temperature profile across the substrate during processing.

SUMMARY

A substrate support assembly comprises a ceramic puck having a substratereceiving surface and an opposing backside surface. The ceramic puck hasan electrode and a heater embedded therein. The heater comprises firstand second coils that are radially spaced apart. A base of the supportassembly comprises a channel to circulate fluid therethrough, thechannel comprising an inlet and terminus that are adjacent to oneanother so that the channel loops back upon itself. A compliant layerbonds the ceramic puck to the base.

In one version, the opposing backside surface of the ceramic puckcomprises a plurality of spaced apart mesas, with first mesas adjacentto the inlet of the channel and second mesas that being distal from theinlet of the channel. The first mesas can be spaced apart a firstdistance that is smaller than a second distance between the second mesasor the first mesas can have a first contact area that is larger than asecond contact area of the second mesas.

DRAWINGS

These features, aspects, and advantages of the present invention willbecome better understood with regard to the following description,appended claims, and accompanying drawings, which illustrate examples ofthe invention. However, it is to be understood that each of the featurescan be used in the invention in general, not merely in the context ofthe particular drawings, and the invention includes any combination ofthese features, where:

FIG. 1 is a schematic side view of an embodiment of a substrateprocessing chamber with the electrostatic chuck;

FIG. 2 is a schematic sectional side view of an embodiment of anelectrostatic chuck;

FIG. 3 is a schematic bottom view of the electrostatic chuck of FIG. 1;

FIGS. 4A and 4B are schematic perspective views of the top (FIG. 4A) andbottom (FIG. 4B) of an embodiment of a base for the electrostatic chuck;

FIG. 5 is a schematic side view of an optical temperature sensor;

FIG. 6A is a schematic sectional side view of a ring assembly on theelectrostatic chuck of FIGS. 4A and 4B;

FIG. 6B is a detail of the ring assembly of FIG. 6A;

FIG. 7 is a graph depicting substrate temperature ramping over aninterval of time with a chiller at a constant temperature;

FIG. 8 is a graph depicting the temperature difference between theelectrostatic chuck and the chiller versus the percentage of heaterpower; and

FIG. 9 is a graph depicting the temperature ramping of the electrostaticchuck.

DESCRIPTION

An exemplary version of a chamber 106 capable of etching a substrate 25is schematically illustrated in FIG. 1. The chamber 106 isrepresentative of a Decoupled Plasma Source (DPS™) chamber which is aninductively coupled plasma etch chamber available from Applied MaterialsInc., Santa Clara, Calif. The DPS chamber may be used in the CENTURA®Integrated Processing System, commercially available from AppliedMaterials, Inc., Santa Clara, Calif. However, other process chambers mayalso be used in conjunction with the present invention, including, forexample, capacitively coupled parallel plate chambers, magneticallyenhanced ion etch chambers, inductively coupled plasma etch chambers ofdifferent designs, as well as deposition chambers. Although the presentapparatus and processes are advantageously used in a DPS chamber, thechamber is provided only to illustrate the invention, and should not beconstrued or interpreted to limit the scope of the present invention.

Referring to FIG. 1, a typical chamber 106 comprises a housing 114comprising enclosure walls 118 that include sidewalls 128, a bottom wall122, and a ceiling 130. The ceiling 130 may comprise a flat shape asshown, or a dome shape with a multi-radius arcuate profile as, forexample, described in U.S. Pat. No. 7,074,723, to Chinn et al., entitled“Method of Plasma Etching a Deeply Recessed Feature in a Substrate Usinga Plasma Source Gas Modulated Etchant System”, which is incorporated byreference herein in its entirety. The walls 118 are typically fabricatedfrom a metal, such as aluminum, or ceramic materials. The ceiling 130and/or sidewalls 128 can also have a radiation permeable window 126which allows radiation to pass through the chamber to monitor processesbeing conducted in the chamber 106. A plasma is formed in a process zonedefined by the process chamber 106, the substrate support and the domedceiling 130.

The substrate 25 is transported by a substrate transport 214 into thechamber 106 and held in the chamber 106 on a receiving surface 26 of asubstrate support 90 comprising an electrostatic chuck 20 which in turnrests on a base 91. The electrostatic chuck 20 comprises a ceramic puck24 having a substrate receiving surface 26 which is the top surface ofthe ceramic puck 24, and serves to hold a substrate 25, as shown inFIGS. 1 and 2. The ceramic puck 24 also has a backside surface 28opposing the substrate receiving surface 26. The ceramic puck 24 has aperipheral ledge 29 having a first step 31 and a second step 33. Theceramic puck 24 comprises at least one of aluminum oxide, aluminumnitride, silicon oxide, silicon carbide, silicon nitride, titaniumoxide, zirconium oxide, and mixtures thereof. The ceramic puck 24 can beunitary monolith of ceramic made by hot pressing and sintering a ceramicpowder, and then machining the sintered form to form the final shape ofthe chuck 20.

It was determined that the thickness of the ceramic puck 24substantially affects the ability to rapidly ramp up and ramp down thetemperature of the substrate. If the ceramic puck 24 is too thick, theceramic puck 24 takes too long to ramp up and down in temperature,causing the temperature of the overlying substrate to take acorrespondingly excessive time to reach the desired set pointtemperature. Further, it was also determined that if the ceramic puck 24is too thin, it does not maintain the substrate at a steady statetemperature and results in substrate temperature fluctuations duringprocessing. Also, the thickness of the ceramic puck 24 affects operationof the electrode 36 which is embedded in the ceramic puck 24. If thethickness of the layer of the ceramic puck 24 directly above theembedded electrode 36 is too high, the electrode 36 does not effectivelycouple energy to the plasma formed in the process zone. On the otherhand, if the thickness of ceramic puck 24 about the electrode 36 is toothin, the RF voltage applied to the electrode 36 can discharge into theplasma creating arcing and plasma instabilities. Thus, the thickness ofthe ceramic puck 24 was precisely controlled to be a thickness of lessthan about 7 mm, for example, a thickness of from about 4 to about 7 mm;and in one version, the ceramic puck had a thickness of 5 mm. At thesethickness levels, the ceramic puck 24 allowed rapid increase anddecrease in the substrate temperature while reducing temperaturefluctuations during the process, and substantially without creatingplasma instabilities.

The electrode 36 embedded in the ceramic puck 24 is used to generate anelectrostatic force to retain a substrate placed on the substratereceiving surface 26, and optionally, to capacitively couple energy tothe plasma formed in the chamber 106. The electrode 36 is a conductor,such as a metal, and be shaped as a monopolar or bipolar electrode.Monopolar electrodes comprise a single conductor and have a singleelectrical connection to an external electrical power source andcooperate with the charged species of the overlying plasma formed in achamber to apply an electrical bias across the substrate held on thechuck 20. Bipolar electrodes have two or more conductors, each of whichis biased relative to the other to generate an electrostatic force tohold a substrate. The electrode 36 can be shaped as a wire mesh or ametal plate with suitable cut-out regions. For example, an electrode 36comprising a monopolar electrode can be a single continuous wire meshembedded in the ceramic puck as shown. An embodiment of an electrode 36comprising a bipolar electrode can be a pair of filled-in C-shapedplates that face one another across the straight leg of the C-shape. Theelectrode 36 can be composed of aluminum, copper, iron, molybdenum,titanium, tungsten, or alloys thereof. One version of the electrode 36comprises a mesh of molybdenum. The electrode 36 is connected to aterminal post 58 which supplies electrical power to the electrode 36from an external power supply 230, which can include a DC voltage powersupply, and optionally, an RF voltage power supply.

Optionally, a plurality of heat transfer gas conduits 38 a,b traversethe ceramic puck 24 and terminate in ports 40 a,b on the substratereceiving surface 26 of the chuck 20 to provide heat transfer gas to thesubstrate receiving surface 26. The heat transfer gas, which can be forexample, helium, is supplied below the substrate backside 34 to conductheat away from the overlying substrate 25 and to the receiving surface26 of the ceramic puck 24. For example, a first gas conduit 38 a can belocated to supply heat transfer gas to a central heating zone 42 a ofthe substrate receiving surface 26, and a second gas conduit 38 b can belocated to supply heat transfer gas to a peripheral heating zone 42 b ofthe substrate receiving surface 26. The central and peripheral heatingzones 42 a,b of the substrate receiving surface 26 of the ceramic puck24 allow corresponding portions of the substrate processing surface 44,for example, the overlying central and peripheral portions 46 a,b of thesubstrate 25 to be maintained at different temperatures to compensatefor non-uniform concentric processing bands that would otherwise occurin the substrate 25 due to corresponding non-uniform bands of processconditions which are different from one another.

The ceramic puck 24 also has an embedded heater 27 to heat the substrate25. The heater 27 comprises a plurality of heater coils 50, 52, forexample, a first heater coil 50 and a second heater coil 52, embedded inthe ceramic puck 24. The temperatures at the central and peripheralheating zones 42 a,b of the substrate receiving surface 26 of theceramic puck 24 are controlled using heater coils 50, 52 which areradially spaced apart and concentric about one another. In one version,the first heater coil 50 is located at a peripheral portion 54 b of theceramic puck 24 and the second heater coil 52 located at a centralportion 54 a of the ceramic puck 24. The first and second heater coils50, 52 allow independent control of the temperatures of the central andperipheral portions 54 a, 54 b of the ceramic puck 24, providing theability to independently control the temperatures of the heating zones42 a,b, to achieve different processing rates or characteristics acrossthe radial direction of the processing surface 44 of the substrate 25.As such, different temperatures can be maintained at the two heatingzones 42 a,b to affect the temperatures of the overlying central andperipheral portions 46 a,b of the substrate 25, thereby counteractingany variable gas species distribution or heat load occurring duringprocessing of the substrate 25. For example, when gas species at theperipheral portion 46 b of the processing surface 44 of the substrate 25are less active than those at the central portion 46 a, the temperatureof the peripheral heating zone 42 b is elevated to a higher temperaturethan the central heating zone 42 a to provide a more uniform processingrates or process characteristics across the processing surface 44 of thesubstrate 25. FIG. 8 demonstrates how the change in the substratetemperature is dependent upon the percentage of heater power supplied bythe inner and outer heating coils embedded in the chuck 20.

In one version, the first and second heater coils 50, 52 each comprisecircular loops of resistive heating elements that are arranged side byside, and can even be substantially in the same plane. For example, theheater coils 50, 52 can each be a continuous concentric loop thatgradually spirals radially inward in the body of the ceramic puck 24. Inone version, the heater comprises a coil having first loops spaced aparta first distance and second loops spaced apart a second distance that isgreater than the first distance. The second loops are positioned about alift pin hole in the puck. The heater coils 50, 52 can also be spiralcoils that spiral about an axis passing through the center of the coils,for example, like a light bulb filament, which are positioned inconcentric circles across the inside volume of the ceramic puck 24. Theresistive heating elements can be composed of different electricallyresistive materials, such as for example, tungsten or molybdenum.

The heater coils 50, 52 have an electrical resistance and operatingpower level that is selected to enhance the rate of ramping up and downthe temperature of the substrate 25. In one version, the heater coils50, 52 each comprise an electrical resistance sufficiently high torapidly rise to and maintain the substrate receiving surface 26 of theceramic puck 24 at temperatures of from about 80 to about 250° C. Inthis version, the electrical resistance of the coils are from about 4 toabout 12 Ohms. In one example, the first heater coil 50 has anelectrical resistance of 6.5 ohm and the second heater coil 52 has anelectrical resistance inner of 8.5 ohm. In another version, the firstand second heater coils comprise a total resistance of less than 10ohms. In one version, the heater comprises a resistance of 8.5 ohms. Theheater coils 50, 52 are powered via independent terminal posts 58 a-dwhich extend through the ceramic puck 24.

In conjunction with the heater coils 50, 52, the pressure of heattransfer gas can also be controlled in the two heating zones 42 a,b torender the substrate processing rates more uniform across the substrate25. For example, the two zones 42 a,b can each be set to hold heattransfer gas at a different equilibrated pressure to provide differentheat transfer rates from the backside 34 of the substrate 25. This isaccomplished by supplying heat transfer gas at two different pressuresthrough the two gas conduits 38 a, 38 b, respectively, to exit at twodifferent locations of the substrate receiving surface 26.

The backside surface 28 of the ceramic puck 24 can have a plurality ofspaced apart mesas 30 as shown in FIG. 3. In one version, the mesas 30are cylindrical mounds that are separated from each other by a pluralityof gaps 32. In use, the gaps 32 are filled with a gas, such as air, toregulate the heat transfer rates from the backside surface 28 to theunderlying surface of the base. In one embodiment, the mesas 30 comprisecylindrical mounds, which can even be shaped as posts, that extend upfrom the backside surface 28, the posts having a rectangular or circularcross-sectional shape. The height of the mesas 30 can be from about 10to about 50 microns, and the diameter of the mesas 30 can be from about500 to about 5000 microns. However, the mesas 30 can also have othershapes and sizes, for example, cones or rectangular blocks, or evenbumps of varying sizes. In one version, the mesas 30 are formed by beadblasting the backside surface 28 with a bead size that is suitablysmall, for example, in the tens of microns, to etch away by erosion thematerial of the backside surface 28 to form the shaped mesas 30 with theintervening gaps 32.

The electrostatic chuck 20 also includes an optical temperature sensor60 a,b that passes through holes 62 a,b in the ceramic puck 24 tocontact and accurately measure the temperatures of the overlying centraland peripheral portions 46 a,b of the substrate 25. A first sensor 60 ais positioned at the central heating zone 42 a of the ceramic puck 24 toread the temperature of the central portion 46 a of the substrate 25,and a second sensor 60 b is positioned at the peripheral heating zone 42b of the ceramic puck 24 to correspondingly read the temperature at theperipheral portion 46 b of the substrate 25. The optical temperaturesensors 60 a,b are positioned in the chuck 20 so that the tips 64 a,b ofthe sensors lies in a plane with the substrate receiving surface 26 ofthe ceramic puck 24, such that the sensor tips 64 a,b can contact thebackside 34 of the substrate 25 held on the chuck 20. The legs 66 a,b ofthe sensors 60 a,b extend vertically through the body of the ceramicpuck 24.

In one version, as shown in FIG. 5, each optical temperature sensor 60comprises a heat sensor probe 68 comprising a copper cap 70 shaped as aclose off cylinder with a side 72 and a dome-shaped top 74 that servesas the tip 64. The copper cap 70 can be composed of oxygen free coppermaterial. A phosphorous plug 76 is embedded inside, and in directcontact with, the dome-shaped top 74 of the copper cap 70. Thephosphorous plug 76 embedded in the copper cap 70 provides quicker andmore sensitive thermal response for the heat sensing probe 68. The tip64 of the copper cap 70 is a dome-shaped top 74 to allow repeatedcontact with different substrates 25 without eroding or damaging thesubstrates. The copper cap 70 has a recessed groove 78 for receivingepoxy 79 to affix the cap 70 in the heat sensing probe 68.

The phosphorous plug 76 converts heat in the form of infrared radiationto photons which are passed though an optical fiber bundle 80. Theoptical fiber bundle 80 can be composed of borosilicate glass fibers.The optical fiber bundle 80 is encased by a sleeve 82, which in turn ispartially surrounded by a temperature isolation jacket 84 that serves toisolate the temperature sensor from the heat of the base that supportsthe ceramic puck. The sleeve 82 can be a glass tubing to provide betterthermal insulation from the surrounding structure, but can also be madefrom a metal such as copper. The temperature isolation jacket 84 may becomposed of PEEK, a polyetheretherketone, and can also be Teflon®(polytetrafluoroethylene) from Dupont de Nemours Co. Delaware.

A substrate support 90 comprising the electrostatic chuck 20 is securedto a coolant base 91 which is used to support and secure the chuck 20,as well as to cool the chuck (FIGS. 4A and 4B). The base 91 comprises ametal body 92 with a top surface 94 having a chuck receiving portion 96and peripheral portion 98. The chuck receiving portion 96 of the topsurface 94 is adapted to receive the backside surface 28 of the ceramicpuck 24 of the electrostatic chuck 20. The peripheral portion 98 of thebase 91 extends radially outward beyond the ceramic puck 24. Theperipheral portion 98 of the base 91 can be adapted to receive a clampring 100 which can be secured to the top surface of the peripheralportion of the base. The metal body 92 of the base 91 has a number ofpassages 102 running from a bottom surface 104 of the base 91 to the topsurface 94 of the base 91, to for example, hold the terminals 58 a-d orfeed gas to the gas conduits 38 a,b of the ceramic puck 24.

The base 91 has a coolant channel 110 comprising an inlet 95 and aterminus 97 to circulate coolant through the channel. The inlet 95 andterminus 97 of the coolant channel 110 can be positioned adjacent to oneanother when the coolant channel 110 loops back upon itself, as shown inFIG. 4B. The coolant may be fluid, such as water, or other suitable heattransfer fluid from a heat transfer fluid supply 220, which ismaintained at a preset temperature in any chiller, and pumped throughthe channel of the base 91. The base 91 with the circulating coolingfluid serves as a heat exchanger to control the temperatures of thechuck 20 to achieve desired temperatures across the processing surface44 of the substrate 25. The fluid passed through the channels 110 can beheated or cooled to raise or lower the temperature of the chuck 20 andthat of the substrate 25 held on the chuck 20. In one version, thechannels 110 are shaped and sized to allow fluid to flow through tomaintain the base 91 at temperatures of from about 0 to 120° C.

The chuck receiving portion 96 of the top surface 94 of the base 91comprises one or more grooves 108 a,b to retain and flow air across thebackside of the ceramic puck 24. In one embodiment, the chuck receivingportion 96 comprises a peripheral groove 108 a which cooperates with aplurality of mesas 30 on the backside surface 28 of a ceramic puck 24 tocontrol a rate of heat transfer from the peripheral portion 54 b of theceramic puck 24. In another embodiment, the chuck receiving surface ofthe base comprises a peripheral groove to contain air about the mesas ofthe backside of the puck. In yet another embodiment, a central groove108 b is used in conjunction with the peripheral groove 108 a toregulate heat transfer from the central portion 54 a of the ceramic puck24.

The grooves 108 a,b in the top surface 94 of the base 91 cooperate withthe mesas 30 on the backside surface 28 of the ceramic puck 24 tofurther regulate the temperatures across the substrate processingsurface 44. The mesas 30 on the backside surface 28 of the ceramic puck24 can be distributed across the backside surface 28 in a uniform ornon-uniform pattern. The shape, size, and spacing of the mesas 30control the total amount of contact surface of the mesas 30 with the topsurface 94 of the base 91 thereby controlling the total heat conductionarea of the interface. When in a uniformly spaced apart pattern, thedistance between the mesas 30 as represented by the gaps 32 remainsubstantially the same, and in a non-uniform spacing, the gap distancevaries across the backside surface 28.

Optionally, the backside surface 28 of the ceramic puck 24 can have afirst array 39 of mesas 30 adjacent to the inlet of the coolant channel110 in the base, and a second array 41 of the mesas 30 distal from theinlet 95 of the channel 110 or even adjacent to the terminus 97 of thecoolant channel 110, as shown in FIG. 3. The second array 41 of mesas 30has a different gap distance forming a different pattern than the firstarray 39 to regulate the heat transfer rates about the regions adjacentto, and distal from the coolant channel 110. For example, a portion ofthe ceramic puck 24 overlying a segment of the coolant channel 110 nearthe channel inlet 95 which receives fresh coolant is often maintained atlower temperatures that the portion of the ceramic puck 24 overlying asegment of the coolant channel 110 near the channel terminus. This isbecause the coolant warms up as it travels through the length of thechannel in the base by capturing heat from the ceramic puck 24. Asresult, the substrate 25 placed on the receiving surface 26 of theceramic puck 24 has a temperature profile with higher temperatures andregions overlying the coolant channel terminus 97 relative to thetemperatures of regions overlying the inlet 95. This temperature profileis compensated for by providing a first array 39 of mesas 30 about thechannel inlet which are spaced apart at a first gap distance, and asecond array 41 of mesas 30 about the channel 110 terminus 97 which arespaced apart at a second gap distance which is different from the firstdistance. When the first distance is larger than the second distance,the heat transfer rate from the portions of the substrate 25 directlyoverlying the first array 39 is lower than the heat transfer rate fromportions of the substrate 25 directly overlying the second array 41.Consequently, heat is transferred away at a slower rate from the firstsubstrate regions than the rate of heat transfer from the secondsubstrate regions causing the first regions to become warmer than thesecond regions to compensate for and equalize the temperature profilethat would otherwise have occurred across the substrate surface 44because of the coolant channel inlet 95 and terminus 97. In one example,the first array 39 of mesas 30 is spaced apart at a first distance of atleast about 5 mm, while the second array 41 of mesas 30 is spaced apartat a second distance of less than about 3 mm.

The same temperature profile control can be obtained by changing thedimensions of the contact regions of first array 39 of mesas 30 relativeto the dimensions of the contact regions of the second array 41 of mesas30. For example, the first dimensions of the contact regions of firstarray 39 of mesas 30 can be less than about 2000 microns, while thecontact regions of the second array 41 of mesas 30 can be at least about3000 microns. The first and second dimensions can be a diameter of amesa 30 comprising a post shape. In one version, the first dimension isa diameter of 1000 microns and the second dimension is a diameter of4000 microns. The less the contact area, the higher the temperaturesacross the substrate processing surface 44. Also, air is providedbetween the mesas 30 and across the backside surface 28 to serve as afurther temperature regulator.

Another factor that affects the ability to rapidly ramp the substrate upand down in temperature is the nature of the thermal interface betweenthe ceramic puck 24 and the base 91. An interface having a good thermalconductivity is desirable at the interface to allow heat to be easilyremoved from the ceramic puck 24 by the coolant traversing through thebase 91. In addition, it is desirable for the interface to be compliantbecause the high temperature differential between the ceramic puck 24and the coolant base 91 results in thermal expansion stresses which cancause cracking or other thermal stress induced damage of the ceramicpuck 24. In one version, a compliant layer 61 is used to bond the backsurface of the ceramic puck 24 to the front surface of the base 91. Thecompliant layer 61 is fabricated to provide good thermal conductivitywhile still being sufficient to compliant to absorb the high thermalstresses. In one version, in the compliant layer 61 comprises siliconwith embedded aluminum fibers. The silicon material provides goodcompliance while still having a reasonable thermal conductivity. Thethermal conductivity of the silicon material is enhanced with theembedded aluminum fibers. In another version, the compliant layer 61comprises acrylic having an embedded wire mesh. Again, the acrylicpolymer is selected to provide compliance with thermal stresses whilethe embedded wire mesh enhances the thermal conductivity of thestructure.

The base 91 further comprises an electrical terminal assembly 120 forconducting electrical power to the electrode 36 of the electrostaticchuck 20 and the first and second heater coils 50, 52, as shown in FIG.6A. The electrical terminal assembly 120 comprises a ceramic insulatorjacket 124. The ceramic insulator jacket 124 can be for example,aluminum oxide. A plurality of terminal posts 58 are embedded within theceramic insulator jacket 124. The terminal posts 58, 58 a-d supplyelectrical power to the electrode 36 and heater coils 50, 52 of theelectrostatic chuck 20. For example, the terminal posts 58 can includecopper posts.

A ring assembly 170 can also be provide to reduce the formation ofprocess deposits on, and protect from erosion, peripheral regions of thesubstrate support 90 comprising the electrostatic chuck 20 supported bythe base 91, as shown in FIGS. 6A and 6B. The ring assembly 170comprises a clamp ring 100 that is secured to the peripheral portion 98of the top surface 94 of the base 91 with securing means such as screwsor bolts (not shown). The clamp ring 100 has a lip 172 which extendstransversely and radially inward, a top surface 174 and an outer sidesurface 176. The lip 172 has an undersurface 173 which rests on thefirst step 31 of the peripheral ledge 29 of the ceramic puck 24 to forma gas-tight seal with the ceramic puck 24, a top surface 174 and anouter side surface 176. In one version, the undersurface 173 comprises apolymer layer 179, for example comprising polyimide, to form a goodgas-tight seal. The clamp ring 100 is fabricated from a material thatcan resist erosion by plasma, for example, a metallic material such asstainless steel, titanium or aluminum; or a ceramic material, such asaluminum oxide.

The ring assembly also includes an edge ring 180 comprising a band 182having a foot 184 which rests on the top surface 174 of the clamp ring100. The edge ring also has an annular outer wall enclosing the outerside surface 176 of the clamp ring 100 which would otherwise be exposedto the processing environment to reduce or even entirely precludedeposition of sputtering deposits on the clamp ring 100. The edge ring180 also comprises a flange 190 covering the second step 33 of theperipheral ledge 29 of the ceramic puck 24 to form a seal with anoverlying edge of a substrate retained on the receiving surface of theceramic puck 24. The flange 190 comprises a projection 194 thatterminates below an overhanging edge 196 of the substrate 25. The flange190 defines an inner perimeter of the ring 180 that surrounds theperiphery of the substrate 25 to protect regions of the ceramic puck 24that are not covered by the substrate 25 during processing. The clampring 100 and the edge ring 180 of the ring assembly 170 cooperate toreduce the formation of process deposits on, and protect from erosion,the electrostatic chuck 20 supported on the base 91 during theprocessing of a substrate 25 in the process chamber 106. The edge ring180 protects the exposed side surfaces of the substrate support 90 toreduce erosion by the energized plasma species. The ring assembly 170can be easily removed to clean deposits from the exposed surfaces of therings 100, 180 so that the entire substrate support 90 does not have tobe dismantled to be cleaned. The edge ring 180 comprises a ceramic, suchas for example, quartz.

In operation, process gas is introduced into the chamber 106 through agas delivery system 150 that includes a process gas supply 204comprising gas sources that each feed a conduit 203 having a gas flowcontrol valve 158, such as a mass flow controller, to pass a set flowrate of the gas therethrough. The conduits feed the gases to a mixingmanifold (not shown) in which the gases are mixed to form a desiredprocess gas composition. The mixing manifold feeds a gas distributor(not shown) 162 having gas outlets in the chamber 106. The gas outletsmay pass through the chamber sidewalls 128 terminate about a peripheryof the substrate support 90 or may pass through the ceiling 130 toterminate above the substrate 25. Spent process gas and byproducts areexhausted from the chamber 106 through an exhaust system 210 whichincludes one or more exhaust ports 211 that receive spent process gasand pass the spent gas to an exhaust conduit in which there is athrottle valve 178 to control the pressure of the gas in the chamber106. The exhaust conduit feeds one or more exhaust pumps 218. Theexhaust system 210 may also contain an effluent treatment system (notshown) for abating undesirable gases that are exhausted.

The process gas is energized to process the substrate 25 by a gasenergizer 208 that couples energy to the process gas in a process zoneof the chamber 106 or in a remote zone upstream from the chamber 106(not shown). By “energized process gas” it is meant that the process gasis activated or energized to form one or more of dissociated gasspecies, non-dissociated gas species, ionic gas species, and neutral gasspecies. In one version, the gas energizer 208 comprises an antenna 186comprising one or more inductor coils 188 which may have a circularsymmetry about the center of the chamber 106. Typically, the antenna 186comprises solenoids having from about 1 to about 20 turns with a centralaxis coincident with the longitudinal vertical axis that extends throughthe process chamber 106. A suitable arrangement of solenoids is selectedto provide a strong inductive flux linkage and coupling to the processgas. When the antenna 186 is positioned near the ceiling 130 of thechamber 106, the adjacent portion of the ceiling 130 may be made from adielectric material, such as silicon dioxide, which is transparent to RFor electromagnetic fields. The antenna 186 is powered by an antennacurrent supply (not shown) and the applied power is tuned by an RF matchnetwork. The antenna current supply provides, for example, RF power tothe antenna 186 at a frequency of typically about 50 KHz to about 60MHz, and more typically about 13.56 MHz; and at a power level of fromabout 100 to about 5000 Watts.

When an antenna 186 is used in the chamber 106, the walls 118 include aceiling 130 made from a induction field permeable material, such asaluminum oxide or silicon dioxide, to allow the inductive energy fromthe antenna 186 to permeate through the walls 118 or ceiling 130. Asuitable semiconductor material is doped silicon. For doped siliconsemiconducting ceilings, the temperature of the ceiling 130 ispreferably held in a range at which the material provides semiconductingproperties and in which the carrier electron concentration is fairlyconstant with respect to temperature. For doped silicon, the temperaturerange may be from about 100 K (below which silicon begins to havedielectric properties) to about 600 K (above which silicon begins tohave metallic conductor properties).

In one version, the gas energizer 208 is also a pair of electrodes (notshown) that may be capacitively coupled to provide a plasma initiatingenergy to the process gas or to impart a kinetic energy to energized gasspecies. Typically, one electrode is in the support 90 below thesubstrate 25 and the other electrode is a wall, for example, thesidewall 128 or ceiling 130, of the chamber 106. For example, theelectrode may be a ceiling 130 made of a semiconductor that issufficiently electrically conductive to be biased or grounded to form anelectric field in the chamber 106 while still providing low impedance toan RF induction field transmitted by the antenna 186 above the ceiling130. A suitable semiconductor comprises silicon doped to have anelectrical resistivity of, for example, less than about 500 Ω-cm at roomtemperature. Generally, the electrodes may be electrically biasedrelative to one another by an a biasing voltage supply (not shown) thatprovides an RF bias voltage to the electrodes to capacitively couple theelectrodes to one another. The applied RF voltage is tuned by an RFmatch network. The RF bias voltage may have frequencies of about 50 kHzto about 60 MHz, or about 13.56 MHz, and the power level of the RF biascurrent is typically from about 50 to about 3000 watts.

The chamber 106 may be operated by a controller 300 comprising acomputer that sends instructions via a hardware interface to operate thechamber components, including the substrate support 90 to raise andlower the substrate support 90, the gas flow control valves 158, the gasenergizer 208, and the throttle valve 178. The process conditions andparameters measured by the different detectors in the chamber 106, orsent as feedback signals by control devices such as the gas flow controlvalves 158, pressure monitor (not shown), throttle valve 178, and othersuch devices, are transmitted as electrical signals to the controller300. Although, the controller 300 is illustrated by way of an exemplarysingle controller device to simplify the description of presentinvention, it should be understood that the controller 300 may be aplurality of controller devices that may be connected to one another ora plurality of controller devices that may be connected to differentcomponents of the chamber 106; thus, the present invention should not belimited to the illustrative and exemplary embodiments described herein.

The controller 300 comprises electronic hardware including electricalcircuitry comprising integrated circuits that is suitable for operatingthe chamber 106 and its peripheral components. Generally, the controller300 is adapted to accept data input, run algorithms, produce usefuloutput signals, detect data signals from the detectors and other chambercomponents, and to monitor or control the process conditions in thechamber 106. For example, the controller 300 may comprise a computercomprising (1) a central processing unit (CPU), such as for example aconventional microprocessor from INTEL corporation, that is coupled to amemory that includes a removable storage medium, such as for example aCD or floppy drive, a non-removable storage medium, such as for examplea hard drive, ROM, and RAM; (ii) application specific integratedcircuits (ASICs) that are designed and preprogrammed for particulartasks, such as retrieval of data and other information from the chamber106, or operation of particular chamber components; and (iii) interfaceboards that are used in specific signal processing tasks, comprising,for example, analog and digital input and output boards, communicationinterface boards, and motor controller boards. The controller interfaceboards, may for example, process a signal from a process monitor andprovide a data signal to the CPU. The computer also has supportcircuitry that include for example, co-processors, clock circuits,cache, power supplies and other well known components that are incommunication with the CPU. The RAM can be used to store the softwareimplementation of the present invention during process implementation.The instruction sets of code of the present invention are typicallystored in storage mediums and are recalled for temporary storage in RAMwhen being executed by the CPU. The user interface between an operatorand the controller 300 can be, for example, via a display and a datainput device, such as a keyboard or light pen. To select a particularscreen or function, the operator enters the selection using the datainput device and can review the selection on the display.

The data signals received and evaluated by the controller 300 may besent to a factory automation host computer. The factory automation hostcomputer may comprise a host software program that evaluates data fromseveral systems, platforms or chambers 106, and for batches ofsubstrates 25 or over an extended period of time, to identifystatistical process control parameters of (i) the processes conducted onthe substrates, (ii) a property that may vary in a statisticalrelationship across a single substrate, or (iii) a property that mayvary in a statistical relationship across a batch of substrates. Thehost software program may also use the data for ongoing in-situ processevaluations or for the control of other process parameters. A suitablehost software program comprises a WORKSTREAM™ software program availablefrom aforementioned Applied Materials. The factory automation hostcomputer may be further adapted to provide instruction signals to (i)remove particular substrates 25 from the etching sequence, for example,if a substrate property is inadequate or does not fall within astatistically determined range of values, or if a process parameterdeviates from an acceptable range; (ii) end etching in a particularchamber 106, or (iii) adjust process conditions upon a determination ofan unsuitable property of the substrate 25 or process parameter. Thefactory automation host computer may also provide the instruction signalat the beginning or end of etching of the substrate 25 in response toevaluation of the data by the host software program.

In one version, the controller 300 comprises a computer program that isreadable by the computer and may be stored in the memory, for example onthe non-removable storage medium or on the removable storage medium. Thecomputer program generally comprises process control software comprisingprogram code to operate the chamber 106 and its components, processmonitoring software to monitor the processes being performed in thechamber 106, safety systems software, and other control software. Thecomputer program may be written in any conventional programminglanguage, such as for example, assembly language, C++, Pascal, orFortran. Suitable program code is entered into a single file, ormultiple files, using a conventional text editor and stored or embodiedin computer-usable medium of the memory. If the entered code text is ina high level language, the code is compiled, and the resultant compilercode is then linked with an object code of pre-compiled libraryroutines. To execute the linked, compiled object code, the user invokesthe object code, causing the CPU to read and execute the code to performthe tasks identified in the program.

In operation, using the data input device, for example, a user enters aprocess set and chamber number into the computer program in response tomenus or screens on the display that are generated by a processselector. The computer program includes instruction sets to control thesubstrate position, gas flow, gas pressure, temperature, RF powerlevels, and other parameters of a particular process, as well asinstructions sets to monitor the chamber process. The process sets arepredetermined groups of process parameters necessary to carry outspecified processes. The process parameters are process conditions,including without limitations, gas composition, gas flow rates,temperature, pressure, and gas energizer settings such as RF ormicrowave power levels. The chamber number reflects the identity of aparticular chamber when there are a set of interconnected chambers on aplatform.

A process sequencer comprises instruction sets to accept a chambernumber and set of process parameters from the computer program or theprocess selector and to control its operation. The process sequencerinitiates execution of the process set by passing the particular processparameters to a chamber manager that controls multiple tasks in achamber 106. The chamber manager may include instruction sets, such asfor example, substrate positioning instruction sets, gas flow controlinstruction sets, gas pressure control instruction sets, temperaturecontrol instruction sets, gas energizer control instruction sets, andprocess monitoring instruction sets. While described as separateinstruction sets for performing a set of tasks, each of theseinstruction sets can be integrated with one another or may beover-lapping; thus, the chamber controller 300 and the computer-readableprogram described herein should not be limited to the specific versionof the functional routines described herein.

The substrate positioning instruction sets comprise code for controllingchamber components that are used to load a substrate 25 onto thesubstrate support 90, and optionally, to lift a substrate 25 to adesired height in the chamber 106. For example, the substratepositioning instruction sets can include code for operating a transferrobot arm (not shown) which transfers a substrate into the chamber, forcontrolling lift pins (not shown) which are extended through holes inthe electrostatic chuck, and for coordinating the movement of the robotarm with the motion of the lift pins.

The program code also include temperature control instruction sets toset and control temperatures maintained at different regions of thesubstrate 25, by for example, independently applying differentelectrical power levels to the first and second heater coils 50, 52 inthe ceramic puck 24 of the chuck 20. The temperature control instructionsets also adjust the flow of heat transfer gas from the heat transfergas supply 222 that is passed through the conduits 38 a,b.

The temperature control instruction sets also comprise code to controlthe temperature and flow rate of coolant fluid passed through thecoolant channels 110 of the base 91. In one version, the temperaturecontrol instruction set comprises code to increase a coolant temperaturein the chiller to a higher level, for at least about one second, from anearlier a lower level, immediately prior to ramping up the power levelapplied to the heater. This allows coolant at a higher temperature to becirculated in the coolant channels of the base 91 just before the heaterincreases temperature to reduce the heat flow from the ceramic puck 24to the base 91 when the heater does eventually rise in temperature,thereby, effectively increasing the temperature ramp up rate of thesubstrate. Conversely, the program code includes instruction sets todecrease the coolant temperature, for example, at least by 10° C. andthe chiller to a lower level prior to ramping down the power levelapplied to the heater to accelerate the rate at which heat istransferred from the substrate when the substrate temperature is rampeddown. The temperature versus time graph in FIG. 7 depicts thetemperature ramp rate for a substrate ramped from 45° C. to 75° C. withthe coolant base maintained at 5° C. FIG. 9 depicts the rapid change insubstrate temperature through the graph of the temperature ramping ofthe electrostatic chuck which holds and imparts heat to the substrate.The substrate maintains the same temperature as the electrostatic chuckby the use of backside helium pressure. The graph demonstrates how theelectrostatic chuck is ramped up and ramped down over a given intervalof time. The two steep hills 291, 293 on the graph indicate the fastramping up and ramping down of the temperature, respectively. Such fasttemperature ramping of the electrostatic chuck allows for rapid changesin the substrate temperature, thus enabling etching of previouslyincompatible materials such as Poly-Si and WSIX.

A process feedback control instruction sets can serve as a feedbackcontrol loop between a temperature monitoring instruction sets whichreceives temperature signals from the optical temperature sensors 60 a,bto adjust the power applied to the chamber components, such as theheater coils 50, 52 from the outer and inner heater power supplies 226,228, respectively, the flow of heat transfer gas through the conduits 38a,b, flow of fluid through the channels 110 of the base 91, and chillercoolant temperature.

The gas flow control instruction sets comprise code for controlling theflow rates of different constituents of the process gas. For example,the gas flow control instruction sets may regulate the opening size ofthe gas flow control valves 158 to obtain the desired gas flow ratesfrom the gas conduits 203 into the chamber 106. In one version, the gasflow control instruction sets comprise code to set a first volumetricflow rate of a first gas and a second volumetric flow rate of a secondgas to set a desired volumetric flow ratio of the first process gas tothe second process gas in the process gas composition.

The gas pressure control instruction sets comprise program code forcontrolling the pressure in the chamber 106 by regulating open/closeposition of the throttle valve 178. The temperature control instructionsets may comprise, for example, code for controlling the temperature ofthe substrate 25 during etching or code for controlling the temperatureof walls of the chamber 106, such as the temperature of the ceiling. Thegas energizer control instruction sets comprise code for setting, forexample, the RF power level applied to the electrodes or to the antenna186.

While described as separate instruction sets for performing a set oftasks, it should be understood that each of these instruction sets canbe integrated with one another, or the tasks of one set of program codeintegrated with the tasks of another to perform the desired set oftasks. Thus, the controller 300 and the computer program describedherein should not be limited to the specific version of the functionalroutines described herein; and any other set of routines or mergedprogram code that perform equivalent sets of functions are also in thescope of the present invention. Also, while the controller isillustrated with respect to one version of the chamber 106, it may beused for any chamber described herein.

The present apparatus and process provides significant benefits byallowing very rapid changes in temperature of the substrate betweendifferent steps of a process performed on the substrate and the chamber.Such rapid temperature changes increase the speed at which an etchingprocess having multiple steps can be performed. The present system alsoallows accurate reproduction of a temperature ramp up and ramp downprofile desirable for a particular process, such as an etching processhaving multiple etching stages which are required for the etching ofdifferent materials or layers on the substrate. Yet another advantage isthat the present apparatus allows maintaining the substrate attemperatures which are significantly higher than the temperature of thecoolant base, which in turns allows the application of higher plasmapower to the substrate without any substrate temperature drift duringthe process. The large temperature difference between the substrate andthe coolant base also allows good temperature differences between theinner and outer zones of the substrate, thereby compensating for varyingannular process conditions across the substrate surface.

Although the present invention has been described in considerable detailwith regard to certain preferred versions thereof, other versions arepossible. For example, the apparatus components such as the substratesupport, coolant base, and temperature sensor can be used for otherchambers and for other processes, than those described herein.Therefore, the appended claims should not be limited to the descriptionof the preferred versions contained herein.

What is claimed is:
 1. A substrate support assembly capable of holdingand heating a substrate in a process chamber, the assembly comprising:(a) a ceramic puck comprising: (i) a substrate receiving surface; (ii)an electrode therein to generate an electrostatic force to retain asubstrate placed on the substrate receiving surface; (iii) a heatertherein to heat the substrate, the heater comprising first and secondheater coils that are radially spaced apart; and (iv) a backside surfacehaving a plurality of shaped mesas that are spaced apart from oneanother and that contact an underlying base, the shaped mesas comprisingposts, cones, rectangular blocks, or cylindrical mounds, and the shapedmesas comprising an array of first mesas that are adjacent to a channelinlet adjacent to a periphery of the base and an array of second mesasthat are adjacent to a channel terminus, and comprising at least one of:(1) the first mesas are spaced apart a first distance that is largerthan a second distance between the second mesas; and (2) the first mesashave a first contact area that is smaller than a second contact area ofthe second mesas; (b) the base comprising a channel to circulate fluidtherethrough, the channel comprising the channel inlet and the channelterminus; and (c) a compliant layer bonding the ceramic puck to thebase.
 2. A support assembly according to claim 1 wherein the ceramicpuck comprises a thickness that is less than 7 mm.
 3. A support assemblyaccording to claim 1 wherein the compliant layer comprises (i) siliconhaving embedded aluminum fibers, or (ii) acrylic having an embedded wiremesh.
 4. A support assembly according to claim 1 further comprising acontroller configured to: (i) independently apply different electricalpower levels to the first and second heater coils; (ii) control thetemperature and flow rate of fluid passed through the channel of thebase; (iii) receive temperature signals from a temperature sensor; and(iv) serve as a feedback control loop to adjust the power applied to thefirst and second heater coils and the flow of fluid through the channelof the base in response to the temperature signals from the temperaturesensor.
 5. A support assembly according to claim 4 wherein thecontroller comprises code to (i) increase a fluid temperature in thebase to a higher level prior to ramping up the electrical power levelsapplied to the heater in the ceramic puck, or (ii) decrease a fluidtemperature in the base to a lower level prior to ramping down theelectrical power levels applied to the heater in the ceramic puck.
 6. Asupport assembly according to claim 4 wherein the temperature sensorcomprises a plurality of optical temperature sensors to measure thetemperatures of central and peripheral portions of a substrate.
 7. Asupport assembly according to claim 6 wherein the optical temperaturesensors include a first sensor positioned at a central heating zone ofthe ceramic puck and a second sensor positioned at a peripheral heatingzone of the ceramic puck.
 8. A support assembly according to claim 1wherein the ceramic puck is composed of aluminum oxide.
 9. A supportassembly according to claim 1 where the first heater coil is located ata peripheral portion of the ceramic puck and the second heater coil islocated at a central portion of the ceramic puck, and wherein the firstand second heater coils are concentric about one another.
 10. A supportassembly according to claim 1 wherein the first heater coil comprisesfirst loops spaced apart a first distance, and the second heater coilcomprises second loops spaced apart a second distance that is greaterthan the first distance.
 11. A support assembly according to claim 10wherein the second loops are positioned about a lift pin hole in theceramic puck.
 12. A substrate support assembly capable of holding andheating a substrate in a process chamber, the assembly comprising: (a) aceramic puck comprising: (i) a substrate receiving surface; (ii) anelectrode therein to generate an electrostatic force to retain asubstrate placed on the substrate receiving surface; (iii) a heatertherein to heat the substrate, the heater comprising first and secondheater coils that are radially spaced apart; and (iv) a backside surfacehaving a plurality of shaped mesas that are spaced apart from oneanother and that contact an underlying base, the shaped mesas comprisingposts, cones, rectangular blocks, or cylindrical mounds, and the shapedmesas comprising an array of first mesas adjacent to a channel inletadjacent to a periphery of the base and an array of second mesas thatare adjacent a channel terminus, the first mesas being spaced apart afirst distance that is larger than a second distance between the secondmesas, and the first mesas having a first contact area that is smallerthan a second contact area of the second mesas; (b) the base comprisinga channel to circulate fluid therethrough, the channel comprising thechannel inlet and the channel terminus; and (c) a compliant layerbonding the ceramic puck to the base.
 13. A support assembly accordingto claim 12 where the first heather coil is located at a peripheralportion of the ceramic puck and the second heater coil is located at acentral portion of the ceramic puck, and wherein the first and secondheater coils are concentric about one another.
 14. A support assemblyaccording to claim 12 wherein the first heater coil comprises firstloops spaced apart a first distance, and the second heater coilcomprises second loops spaced apart a second distance that is greaterthan the first distance.
 15. A support assembly according to claim 12wherein the ceramic puck comprises a thickness of less than 7 mm.
 16. Asubstrate support assembly capable of holding and heating a substrate ina process chamber, the assembly comprising: (a) a ceramic puckcomprising a substrate receiving surface and an opposing backsidesurface, the ceramic puck comprising (i) an electrode in the ceramicpuck to generate an electrostatic force to retain a substrate placed onthe substrate receiving surface, and (ii) a heater in the ceramic puckto heat the substrate, the heater comprising first and second heatercoils that are radially spaced apart; (b) a base comprising a channel tocirculate fluid therethrough, the channel comprising an inlet andterminus; (c) a compliant layer bonding the ceramic puck to the base;and (d) a controller configured to (i) independently apply differentelectrical power levels to the first and second heater coils, (ii)control the temperature and flow rate of fluid passed through thechannel of the base, (iii) receive temperature signals from atemperature sensor, and (iv) serve as a feedback control loop to adjustthe power applied to the first and second heater coils and the flow offluid through the channel of the base in response to the temperaturesignals from the temperature sensor, and wherein the controller isprogrammed to (1) increase a fluid temperature in the base to a higherlevel prior to ramping up the electrical power levels applied to theheater in the ceramic puck, or (2) decrease a fluid temperature in thebase to a lower level prior to ramping down the electrical power levelsapplied to the heater in the ceramic puck.
 17. A support assemblyaccording to claim 16 wherein the backside surface of the ceramic puckcomprises a plurality of shaped mesas that are spaced apart from oneanother and that contact the underlying base, the shaped mesascomprising first mesas that are adjacent to a channel inlet adjacent toa periphery of the base and second mesas that are adjacent to a channelterminus, and comprising at least one of: (1) the first mesas are spacedapart a first distance that is larger than a second distance between thesecond mesas; and (2) the first mesas have a first contact area that issmaller than a second contact area of the second mesas.
 18. A supportassembly according to claim 1 wherein the shaped mesas comprise at leastone of: (i) a height of from about 10 to about 50 microns; and (ii) adiameter of from about 500 to about 5000 microns.
 19. A support assemblyaccording to claim 1 comprising at least one of: (i) the first mesashave contact regions with a dimension of less than 2000 microns; and(ii) the second mesas have contact regions with a dimension of at leastabout 3000 microns.
 20. A support assembly according to claim 12comprising at least one of: (i) the shaped mesas have a height of fromabout 10 to about 50 microns; (ii) the shaped mesas have a diameter offrom about 500 to about 5000 microns; (iii) the first mesas have contactregions with a dimension of less than 2000 microns; and (iv) the secondmesas have contact regions with a dimension of at least 3000 microns.